Pros and cons of wood cellulose binders for 4.6 V LiCoO₂ lithium-ion batteries

Raising the charging cutoff voltage of LiCoO₂ cathode is an effective route to boost the energy density of lithium-ion batteries. However, when operated above 4.5 V, LiCoO₂ electrode suffers from accelerated structural degradation and severe interfacial side reactions, leading to rapid capacity fading. Conventional PVDF binders offer limited protection under such high-voltage conditions due to their weak interfacial adhesion and chemical inertness, underscoring the need for more robust alternatives. Here, wood cellulose nanofibers are introduced as a multifunctional binder for high-voltage LiCoO₂ cathodes. Benefiting from its nanofibrous network and abundant functional groups, the cellulose binder yields a uniform, conductive coating that enhances Li⁺ transport and suppresses electrolyte-induced degradation. As a result, the cellulose-based LiCoO₂ electrode delivers 91.1% capacity retention after 100 cycles at 4.6 V, significantly outperforming the PVDF counterpart. Moreover, material characterization confirms partial electro-degradation of the cycled cellulose binder, primarily through scission of glycosidic and carboxyl bonds. This work demonstrates the feasibility of employing aqueous nanocellulose binders for high-voltage cathodes and provides mechanistic insights to guide the molecular design of chemically stabilized cellulose materials for next-generation high-energy lithium-ion batteries.